Pressure responsive indicating device



.Feb. 8, 1949. w. E. NAYLOR 2,461,075

PRESSURE RESPONSIVE INDICATING DEVICE Filed Oct. 12, 1945 6| V IBM: 60 3 :55 w/LLHM A /wmfi 52 L63 BY ATTORN EY Patented Feb. 8, 194a raassuaa aasronsrvn mmcs'rmo DEVIC William E. Naylor, ltldgeileld Park, N. 1., asaignor to Bendix Aviation Corporation, Teterboro, N. 1., a corporation of Delaware Application October 12, 1945, Serial No. 622,024

1 Claim.

This invention relates to a pressure actuated alarm mechanism; and more particularly to an alarm mechanism for cabin planes, actuated by the varying barometric pressure due to the changes in altitude, to warn the pilot or the plane occupants of the lower and upper altitude limits within which oxygen is required.

An object of this invention is to provide an alarm mechanism in which the expansion and/or contraction of an aneroid will open and close an electrical circuit to set oi! an alarm.

Another object of the present invention is to provide anialarm of the character described with coarse and fine control contacts, the coarse contacts closing at approximately the present altitude while the line contacts close at the exact present altitude to complete the alarm circuit.

A further object of my present invention is to provide an alarm mechanism of the character described with a relay actuated alarm circuit hava ing means to hold said circuit energized after the coarse or fine contacts open due to changes in plane altitude, the alarm circuit holding means being rendered inoperative upon actuation of a switch in the relay circuit.

Yet another object of this invention is to provide an alarm mechanism of the character described which shall be corrected for varying temperatures encountered at diii'erent flight altitudes. V

Still another object of this invention is to provide a highly improved, compact and rugsed alarm mechanism of the character described which shall be relatively inexpensive to manufacture, easily installed, positive in action, which shall have a large variety of applications and yet be practical and efficient to a high degree in use.

' sponsive alarm mechanism embodying the invention,

Figure 2 is another perspective view of the alarm mechanism,

Figure 3 is a schematic wiring diagram for the alarm mechanism,

Figure 4 is an enlarged sectional view of a bimetal pivot support, while Figure 5 is an enlarged sectional view of a second bimetal pivot support.

Referring now in detail to Figures 1 and 2, ll designates a pressure responsive alarm mechanism embodying the present invention. The mechanism III is mounted on two horizontal parallel plates II and i2 fixed to each other and spaced apart as by the two spacers i3 and a standard ll. Fixed to the standard it by suitable means is a double bellows aneroid i5.

Journaled in a suitable bearing l6 fixed to the bottom plate i2, is a jack shaft l'l extending upwardly and parallel to the two spacers ii; the upper end of said jack shaft extending through a suitable opening '(not shown) .in the top plate ii. Fixed to the shaft i1 is a hub is about which is coiled a centering spring it. One end of said spring is fixed to said hub while the other end is fixed to a spacer l3, as by screw 20.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements and arrangement of parts which will be exemplified in the construction hereinafter described and of which the scope of application will be indicated To correct the expansion of the aneroid ii for temperature variations so that the alarm system may function at the proper altitude regardless of temperature changes, the pivots used for interconnecting the aneroid and the shaft i! are both fixed to suitable bimetal mountings.

Inserted through an enlarged section II of shaft H is a threaded stud 5 which carries a formed, bimetal strip 22, (Figure 4). Fixed to the turned end of said strip is a bifurcated lug I provided with a pivot pin 81. The stud may be moved by turning nut I2 to vary the distance between the center line of the shaft I1 and the pivot pin 6'! to permit a finer calibration by changing the angular movement of the shaft. After adjustment, the stud G5 is locked in place by a set screw 13.

Fixed to the center of aneroid I! is a small plate 6| carrying a horizontal stud It. Rotatably mounted in a suitable opening in said stud is a bimetal rod 10 (Figure 5). Fixed to the rod and coaxial therewith is a pivot pin II. The bimetal rod may be rotated to adjust the center line of thepin IItobeindirectlinewiththelinea'r movement of the aneroid upon expansion thereof under all temperature conditions encountered. As indicated in Figure 5 the most suitable position for the bimetal rod is when the line made by the joining of the two metals is approximately 45 from the plane of the face of aneroid II. In this manner the travel oi the pin 28 off the line of aneroid movement is kept ata minimum durin: temperature changes.

A link 28 pivoted on the pins 81 and 28 intere connects the aneroid l5 and the shaft i1 to os-' cillate the same upon expansion and contraction of the aneroid due to the barometric pressure changes.

Means is now provided to utilize the oscillation of the shaft l1 to engage and disengage electrical circuit-making elements.

. To this end, there is affixed to the top plate ll adjacent to the upper end of the jack shaft i1, 88

by screws 25, an insulation block 28 made of suitable insulation material such as Bakelite or nylon.

The insulation block 28 is provided with two metal inserts 21 and 28, the end faces of said inserts being flush with the top surface of the insulation block. .The two inserts 'are'connected electrically in series by 'two horizontal binding posts 28 inserted into the block 25 to engage sai inserts, and by a wire 80.

Fixed to the, upper end of the shaft i1, asby screw 81, is a wiper, contact 82 adapted to engage Upon expansion of the aneroid I5, shaft n will proximately 10,000 feet, and disengage said insert at approximately 10,500 feet. To eliminate the error in altitude, the fine adjustment disc 88 upon its rotation and engagement of the insert 8| by the brushes 88 will correct the altitude to an exact 10,250 feet. As will hereinafter appear, an alarm circuit will thus be completed at the 10,250 feet altitude preset into the mechanism. The higher altitude insert 28 will operate in theme manner as heretofore described at the 40,500 feet altitude.

jj-Referring now to Figure 3, the wire 88 interconnects one of the brushes 85 with a relay coil 81. The other end of the relay coil 81 is connected by wire 88 to one side of the battery 88, the other of a'push-button switch 81, through said switch be rotated in a. counter-clockwise direction (Fig- Means is now provided to complete an alarm circuit by a vernier mechanism at the exact 'altitude for which the alarm is set.

.To this end there is fixed to-the Jack shaft I1 a sector gearv 85 having its own small counter weight 38. J ournaled in a suitable bracket 81 and through the top platei I, is a shaft 88 to which is afilxed a pinion 39 meshing withthe teeth of the sector gear 85. Fixed to the shaft 38 above plate II, isa small insulation disc 80 provided witha metal insert 81,- The insulation disc 80 is pro-' exposing a vided with two peripheral grooves 82 minute segment of themetal insert 8t.

Fixed to the top plate H by a screw 88, isa contact holder -88 made' 'ofin'sulation material and retaining .two brushes 85. Brushes 85- are adapted to ride in the peripheral grooves. 82 in.

said disc-80 andengage'the exposed segments of the metal insert;v Oneof saidbrushes is connected to the wirefll-interconnecting the two inserts 2'! and". The other of said'b'ru'shes is .coni'rectedto'a wire 88. .1 i

'In the present'embodiment of the invention, the

relative movement of the. disc 88 and the wiper arm' 82 isapproximately' 20 to,.1. The movement of the wiper arm 32 may be called the coarse altitude adjustment while the movement of the disc 88 may be called the fine altitude adjustment. The wiper arm 82 will engage the insert 21 at apthe brushes 85 disengage the insert 8|.

alarm circuit will remain closed until the pushand by wire 58 to the wire 58. s The stationary contact 58 is connected by wire 58 to the wire 88. Switch arm 52 is connected by-wire tifthrough eh gized when the wiper arm 32 engages either of the inserts 21and 28and brushes 85 engage insert 8|. Upon ener'gizationof the relay 81, switch arm II.

'will engage the stationary contact 58 to complete aholding circuit for said relay through the pushbutton switch 51. At the same time, switch arm 52 will engage the stationary contact 55 to complete the electrical circuit for the alarm 8|. The relay coil 81 will thus remain. energized and actuate the alarm 8i even though the wiper arm 82 disengages either of the inserts 21 or 28; or when The button switch 51 is opened tobreak the holding circuit of the relay coil.

.It will thus be seen that there is provided a pressure actuated alarm device in which the several-objects of this invention are achieved, and which is well adapted to meet the conditions of practical use. r, I

As various possible embodiments might be made of the above invention, and as various changes might be made int-he embodimentv set forth, it is to be understood that all matters herein set forth, or shown in thejaccompanying drawings, are to be interpreted as illustrative, and not in a limiting 'Having thus described my invention, I claim as new and desire to secure by Letters Patentr A pressure responsive device comprising, a pressure responsive member adapted to be actuated by varying pressures, a shaft adapted to be oscillated by said memben a wiper arm on said. shaft, at least two electricalcontacts spacedapartfrom eachother adapted to be engaged, by said wiper arm-upon movement by said shaft, the spacing of said contacts being representative. of different pressure conditions; an insulation disc rotated by said shaft, the angular displacement of said disc being greater than the angular displacement of said shaft by said members; an electrical conducting insert in said disc close to peripheral edge thereof, two peripheral grooves in'said disc to expose two segments of said insert. a pair of brushes 5 i 6 cooperating with said grooves adapted to engage simultaneously the exposed segments of said in- REFERENCES cnED sert, an electrical circuit includin said contacts, Th followin references re of record in the wiper arm, insert and brushes; a relay coil in said file of this patent: circuit adapted to be energized upon concurrent UNITED STATES PATENTS engagement of at least one of said contacts by said wiper arm and said insert by both of said Number Name Date brushes, and means actuated by the energized re- 839,533 Mail's m 1908 lay coil 'to indicate a pressure condition repre- 2,278939 Muehter AD 1942 sented by the contact engaged by said wiper arm. m 2,302,072 Tickell NOV. 17, 1942 WILLIAM NAY1' ,QR 2,316,411 Finnegan Apr. 13, 1943 

